In this section we will learn how to find the percentage of a given number :
To find the % of a given number use the following steps :
1) Obtain the number, say x.
2) Let the percent as p%.
3) P% of x
4) write these as a proportion as p/100 = ?/x
5) Now cross multiply and find the value of "?" mark.
Examples :
1) 30 % of 180
Solution :
30/100 = x/180
Cross multiply
100x = 30 . 180
100x = 5400
∴ x = 5400/100
= 54
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2) 75 % of 400
Solution :
75/100 = x/400
Cross multiply
100x = 75 . 400
100x = 30,000
X = 30,000/100
x = 300
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3) 3 ⅓ of 90 km
Solution :
3 ⅓/100 = x/90
(10/3)/100 = x/90 [ convert mixed fraction to improper]
10/300 = x/90
Cross multiply
300x = 10 . 90
300x = 900
x = 900/300
x = 3 km
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4) 2.5 % of 800 meters
Solution :
2.5/100 = x/800
Cross multiply
100x = (2.5) . 800
100x = 2,000
x = 2,000/100
x = 2 meters
______________________________________________________________ Another method
1) 5% of $1400
Solution :
5 % of 1400
As there is a % sign with 5 so write 5% as 5/100, "of" means multiplication so multiply by 1400.
(5/100) x 1400
(5 x 1400)/100
7,000 /100
=$70
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2) 16 % of 25 liters.
Solution :
16 % of 25
As there is a % sign with 16 so write 16% as 16/100, "of" means multiplication so multiply by 25.
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